Nutrient uptake as a contributing explanation for deep rooting in arid and semi-arid ecosystems
Nutrient uptake as a contributing explanation for deep rooting in arid and semi-arid ecosystems
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DOI：
10.1007/s00442-004-1687-z
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发表时间：
2004-12-01
期刊：
影响因子：
2.7
通讯作者：
Jackson, RB
中科院分区：
文献类型：
--
作者：
McCulley, RL;Jobbágy, EG;Jackson, RB
传统上，对干旱和半干旱生态系统中深根植物的出现的解释强调了相对深层土壤水分的吸收。然而，最近从干旱系统的水文数据表明，土壤水的潜力在很长一段时间内波动很小，这表明这种水可能很少被利用或补充。在这项研究中，我们研究了分布在美国西南部的5个半干旱和干旱地区的根生物量，土壤水分和养分含量的10米深处。我们将这些深度分布与锶（Sr）同位素数据相结合，这些数据表明，五个站点中有四个站点的深层（> 1 m）营养吸收普遍存在。在所有地点，一种或多种测量的营养物质的最高丰度出现在土壤剖面深处，特别是P、Ca 2+和Mg 2+。磷酸盐含量在深度大于在顶部米的土壤在三个五个站点。例如，在Jornada，2 - 3米深度增量的可提取磷是土壤顶层米的两倍，尽管表层的磷浓度最高。这种深资源池的普遍性，以及我们的证据，从他们的阳离子吸收，营养吸收作为一个补充解释深根植物在干旱和半干旱系统的发生。我们认为，浅层地表水通过根系向深层土壤的水力再分配可能是深层土壤养分被植物动员和吸收的机制。
Explanations for the occurrence of deep-rooted plants in arid and semi-arid ecosystems have traditionally emphasized the uptake of relatively deep soil water. However, recent hydrologic data from arid systems show that soil water potentials at depth fluctuate little over long time periods, suggesting this water may be rarely utilized or replenished. In this study, we examine the distributions of root biomass, soil moisture and nutrient contents to 10-m depths at five semi-arid and arid sites across southwestern USA. We couple these depth distributions with strontium (Sr) isotope data that show deep (> 1 m) nutrient uptake is prevalent at four of the five sites. At all of the sites, the highest abundance of one or more of the measured nutrients occurred deep within the soil profile, particularly for P, Ca2+ and Mg2+. Phosphate contents were greater at depth than in the top meter of soil at three of five sites. At Jornada, for example, the 2 - 3 m depth increment had twice the extractable P as the top meter of soil, despite the highest concentrations of P occurring at the surface. The prevalence of such deep resource pools, and our evidence for cation uptake from them, suggest nutrient uptake as a complementary explanation for the occurrence of deep-rooted plants in arid and semi-arid systems. We propose that hydraulic redistribution of shallow surface water to deep soil layers by roots may be the mechanism through which deep soil nutrients are mobilized and taken up by plants.